A multivariate probabilistic approach for tracking seasonally and longitudinally the Intertropical Convergence Zone
Abstract
The location of the Intertropical Convergence Zone (ITCZ) and its seasonal shift controls precipitation patterns in the tropics and subtropics, and greatly affects the vulnerability of ecosystems and rainforests. On average, the ITCZ lies in the northern hemisphere, yet its exact position and seasonal migration vary along different longitudes. On multidecadal scales, the position of the ITCZ is influenced by the interhemispheric temperature contrast, or more generally, the interhemispheric energetic asymmetry of the globe, and it tends to move toward the warmer hemisphere, mimicking its seasonal migration.
Due to its importance for water availability, efficient tracking of the seasonal and long-term shifts of ITCZ is of great value. Current approaches which are based on tracing changes in the annual mean of single variables (like precipitation) do not facilitate analysis of changes in the within-year dynamics, while more sophisticated methods are computationally intensive. Here we propose a new probabilistic framework to track the ITCZ, which is based on jointly tracking the location of maximum precipitation and minimum outgoing longwave radiation in overlapping longitudinal windows. Our framework is seasonally and longitudinally explicit, allows for joint consideration of multiple variables to define the ITCZ, and is flexible in its implementation, thus, it can be used in analyses of different scales and scopes. We apply our framework to analyze the recent climatology of the ITCZ and long-term trends in its dynamics since the mid 19th century. We report an increased frequency of ITCZ migration to the southern central Pacific in recent decades relatively to the past.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A51K2314M
- Keywords:
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- 0321 Cloud/radiation interaction;
- ATMOSPHERIC COMPOSITION AND STRUCTUREDE: 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 3373 Tropical dynamics;
- ATMOSPHERIC PROCESSESDE: 3374 Tropical meteorology;
- ATMOSPHERIC PROCESSES